The invention relates generally to sorbents and, more specifically, to an inexpensive K—Fe-based sorbent developed using K2CO3 and nanoporous FeOOH.
People are increasingly concerned about the climate changes we have experienced; including the increases in global average air and ocean temperatures, rising sea levels, and widespread melting of ice caps and glaciers. Rising global temperatures could lead to many disasters including severe weather events, drought and flooding, and thus food supply shortfalls, lack of water security, deterioration of ecosystems, and spread of vector-borne diseases.
The main greenhouse gases associated with climate changes are carbon dioxide, methane, nitrous oxide and some halogenated compounds. The quantity of CO2 emitted to the atmosphere due to human activities is much greater than those of other greenhouse gases. As a result, CO2 makes the greatest contribution to the greenhouse effect despite its low unit globe warming potential. According to the latest analyses of the data from the global greenhouse gas monitoring network of World Meteorological Organization (WMO), the global concentration of CO2 in the atmosphere reached a new high level in 2009, 386.8 ppm, which is ˜38% higher than those in pre-industrial times.
Net CO2 emission reductions could be achieved by reducing energy consumption through increasing energy conversion efficiency, switching to less carbon-intensive fuels, and using alternative fuels. However, fossil fuels, such as coal, oil and natural gas, are likely to continue to be used for meeting more than 80% of total world energy demand in the coming decades due to their high energy densities and wide availabilities. The capture and storage of carbon dioxide will be the major method to be used for limiting CO2 emissions from the combustion of fossil fuels in this century.
A variety of methods, such as membrane separation, absorption with a solvent, and cryogenics techniques, have been used to separate CO2 from flue gases and other waste gas streams. These methods, however, are energy-intensive. Regenerable solid sorbents containing inexpensive alkali metals and alkali earth metals have attracted many people's attention since they could be regenerated with the heat recovered from the waste gas streams including flue gas and thus could provide cost-effective approaches to removal of CO2 from flue gas in power plants. A major challenge in developing solid CO2 sorbents is to find new multifunctional supporting materials for alkali chemicals such as potassium carbonate. Several studies have been conducted on separation of CO2 from the simulated flue gas steams with K2CO3 supported by TiO2, SiO2, CaO, MgO and different porous matrices such as activated carbon, silica gel, aluminum oxide, and vermiculite under cyclic fixed-bed operation conditions along with the presence of H2O. However, nanoporous FeOOH has not been tested by others as a supporting material for synthesis of a solid CO2 sorbent. In this research, a new K—Fe solid sorbent has been developed using low-price potassium carbonate and nanoporous multifunctional FeOOH. The performance of the K—Fe sorbent on CO2 sorption and desorption was evaluated using a fixed bed reactor under different operation conditions, and the associated sorption and desorption mechanism, thermodynamics as well as kinetics were investigated.